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Bureau of Mines Information Circular/1987 



Assessment and Determination 

of Illumination Needs for Operators 

of Mobile Surface Mining Equipment 



By Alan G. Mayton 




UNITED STATES DEPARTMENT OF THE INTERIOR 




Information Circular 9153 

n 



Assessment and Determination 

of Illumination Needs for Operators 

of Mobile Surface Mining Equipment 



By Alan G. Mayton 



UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 

David S. Brown, Acting Director 







Library of Congress Cataloging in Publication Data: 



Mayton, Alan G. 

Assessment and determination of illumination needs for operators 
of mobile surface mining equipment. 

(Information circular/Bureau of Mines; 9153) 

Bibliography: p. 30. 

Supt. of Docs, no.: I 28.27: 9153. 

1. Mine lighting. 2. Strip mining — Equipment and supplies. I. Title. II. Series: 
Information circular (United States. Bureau of Mines); 9153. 

TN295.U4- [TN301] 622 s [622'.47] 87-600143 



CONTENTS 

Page 

Abstract 1 

Introduction 

Acknowledgments 

Description and procedures 2 

Field measurements 3 

VTE description and principle of operation . .... 3 

CIE-IES method 5 

Discussion and results 5 

Surface coal mines 6 

Draglines 6 

Stripping and loading shovels 8 

Loaders 11 

Haul trucks 11 

Blasthole drills 12 

Explosives trucks 14 

Scrapers 14 

Bulldozers 18 

Graders 18 

Service vehicles 21 

Surface metal and nonmetal mines 24 

Conclusions and recommendations 26 

References 30 

Appendix A. — Glossary of terms, abbreviations, and symbols 31 

Appendix B. — Calibration and analysis procedures 33 

ILLUSTRATIONS 

1. Blackwell model 5, serial No. 2, visual task evaluator (VTE) 3 

2 . Outer rectangular lens units of VTE 4 

3. Minolta 1° luminance meter and RS-1 reflectance standard 4 

4. Munsell charts, multicolored chips for judging reflectance 5 

5. Typical lighting on dragline operating during nighttime hours 7 

6. Stripping shovel with typical lighting system 8 

7. Typical illumination on loading shovel 10 

8. Typical lighting system on loader 10 

9. Haul truck dumping load at waste dump 12 

10. Typical illumination on blasthole drill 14 

11. Flatbed truck for transporting packaged explosives 16 

12. Tank- or drum-type truck for transporting bulk mixture of explosives 16 

13. Typical lighting on scraper 17 

14. Typical lighting on bulldozer 21 

15. Typical illumination system on motor grader 21 

16. Truck used for refueling and lubricating equipment 23 

17. Luminaires mounted on top rear section of lubrication truck 23 

18. Typical portable lighting unit 30 

B-l. Contrast control calibration for VTE model 5 33 

B-2. Normal population data to determine calibration constant for users of VTE 

model 5 34 

B-3. Correction constant for VTE model 5 35 



ii 



TABLES 



Page 



Illumination values resulting from task visibility measurements for — 

1 . Coal mine draglines 7 

2. Coal mine shovels 9 

3 . Coal mine loaders 11 

4. Coal mine haul trucks 13 

5. Coal mine blasthole drills 15 

6. Coal mine explosives trucks 17 

7. Coal mine scrapers 18 

8. Coal mine bulldozers 19 

9. Coal mine motor graders 22 

10. Coal mine fuel trucks 24 

11. Coal mine lubrication trucks 25 

12. Coal mine water truck 25 

13. Noncoal mine shovels 27 

14. Noncoal mine blasthole drills 28 

15. Noncoal mine loaders 29 





UNIT OF MEASURE 


ABBREVIATIONS 


USED 


IN 


THIS 


REPORT 


cd/m 2 


candela per square 


meter 






in 


inch 


deg 


degree 










lx 


lux 


fc 


footcandle 










mph 


mile per hour 


fL 


footlambert 










s 


second 


ft 


foot 










yr 


year 


h/d 


hour per day 















ASSESSMENT AND DETERMINATION OF ILLUMINATION NEEDS FOR 
OPERATORS OF MOBILE SURFACE MINING EQUIPMENT 

By Alan G. Mayton 1 



ABSTRACT 

The Bureau of Mines conducted one of the most extensive studies on 
surface mine illumination to date, to assess the illumination needs of 
mobile surface mining machinery with respect to the visual tasks re- 
quired of machinery operators. Field investigations were performed at 
22 surface mining operations, coal and metal-nonmetal, within several 
mining regions of the United States. Visibility and illumination were 
measured for 159 visual tasks performed by equipment operators on or 
near 57 surface mining machines, including draglines, shovels, blasthole 
drills, bulldozers, loaders, haul trucks, graders, scrapers, and several 
service-type vehicles. 

The report shows that illumination and/or visibility could be improved 
for various visual tasks and makes recommendations for these improve- 
ments. Moreover, the report describes the various equipment studied, 
gives details of the instruments and measuring techniques used, and pre- 
sents equations to calculate the luminance and illuminance levels sug- 
gested for performing mining tasks. Tables are presented that compare 
values of illumination computed for workers in the 25- and 50-yr age 
groups. Appendixes to the report includes a glossary of terms, abbrevi- 
ations, symbols, and calibration and analysis procedures. 

1 Mining engineer, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 



INTRODUCTION 



Surface mines, which can cover many 
square miles of land, use very large, 
electric- or diesel-powered, mobile con- 
struction-type equipment. Most surface 
mines run their machinery 24 h/d to meet 
production quotas and to recover costs of 
capital investments. When persons work 
on or about equipment of this size and 
power, safety is obviously a major con- 
cern. When work activities take place 
during nighttime hours, safety practices 
take on an important dimension — the 
provision for proper and effective 
illumination. 

Since the passage of the Coal Mine 
Health and Safety Act of 1969, the Bureau 
of Mines has played a major role in illu- 
mination research and in the development 
of illumination criteria and technology 
to provide adequate lighting for workers 
in U.S. mining operations. This has been 
accomplished most notably in underground 
coal mining, and to a degree, in surface 
mining. 

In 1977, the Mining Enforcement and 
Safety Administration (MESA) under the 
Department of the Interior (now the Mine 
Safety and Health Administration (MSHA) 



under the Department of Labor) proposed 
mandatory safety standards of illumina- 
tion for surface coal mines and surface 
work areas of underground coal mines 



(1). 



These standards, however, were 



never approved. In 1981, the Inter- 
national Commission on Illumination (CIE) 
began to focus attention on illumination 
standards for surface mining by estab- 
lishing a program to develop recommenda- 
tions for opencast (surface mine) light- 
ing. Concurrent with its involvement 
with the CIE and in view of the lack of 
approved lighting standards, the Bureau 
initiated a program to study illumination 
on mobile surface mining equipment from 
the viewpoint of the equipment operators. 
The objective of the program was to as- 
sess the illumination needs of various 
surface mining equipment on the basis of 
the visibility required by workers in 
performing the necessary visual tasks as- 
sociated with their jobs. Overall, the 
intent of the study was to provide useful 
data and information for MSHA and the CIE 
to use in establishing lighting standards 
and recommending lighting practices for 
surface mines. 



ACKNOWLEDGMENTS 



The author thanks C. L. Crouch, presi- 
dent of CLC Associates, Floral Park, NY, 
and Port Charlotte, FL, for his assist- 
ance with the collection and analysis of 
the data. The author also thanks H. R. 



Blackwell, president of Visioneering Lab- 
oratories, Sarasota, FL, and Frankfurt, 
MI, for his cooperation and assistance 
with the visual task evaluator (VTE) 
instrumentation. 



DESCRIPTION AND PROCEDURES 



The study was conducted using a VTE (a 
visibility meter, described in detail la- 
ter) according to the methods and prac- 
tices recommended by the CIE and the Il- 
luminating Engineering Society of North 
America (IES). The main program effort 
involved the collection of visibility and 
illumination data through on-site visits 
to various surface mines and quarries in 
several mining regions of the United 
States. Field investigations were con- 
ducted at 22 different surface mining 



operations in Michigan, Indiana, Alabama, 
Florida, Ohio, Massachusetts, New Hamp- 
shire, and New York. Useful data were 
obtained from 12 of them: 5 metal and 
nonmetal (M-NM) mines and quarries and 7 
coal mines. The M-NM operations included 
two iron ore mines and three limestone 

2 Underlined numbers in parentheses re- 
fer to items in the list of references 
preceding the appendixes. 



quarries. 3 The visual tasks of equipment 
operators were identified on or about 57 
surface mining machines, including quarry 
equipment. The equipment included drag- 
lines, shovels, blasthole drills, bull- 
dozers, loaders, haul trucks, graders, 
scrapers, lubrication trucks, fuel 
trucks, and a water truck. Visibility 
was measured for 159 tasks using the 
Blackwell model 5 VTE. 4 The existing il- 
lumination was determined using the re- 
flectance standard RS-1 (a barium sulfate 
plaque with a nominal reflectance of 98%) 
and the Minolta 1° luminance meter. 

FIELD MEASUREMENTS 

After a visual task of a particular 
equipment operator was identified, the 
VTE (fig. 1) was set up in the location 
from which the operator would normally 
view the critical detail of the task. 
The approximate angular position of the 
VTE and the approximate distance from the 
outer lens of the VTE to the object or 
surface of interest were estimated or 
measured and recorded. The proper outer 
lens unit (fig. 2) was selected based on 
the measured (or estimated) distance and 
attached to the front of the VTE. Then, 
no fewer than five readings were obtained 
while looking through the VTE and turning 
the contrast control dial. After the VTE 
readings were taken, the luminances of 
the target (critical detail of the task) 
and its background were measured with the 
Minolta meter. The illuminance or illu- 
mination of the task was determined 
by measuring the luminance of the RS-1 
plaque (placed on or directly above the 

3 Ten other M-NM operations were vis- 
sited. However, the visibility and illu- 
mination data from two granite quarries 
and two limestone quarries are not in- 
cluded because the VTE was later found to 
be out of calibration. Also, it was not 
possible to obtain visibility measures at 
five phosphate mines and one other lime- 
stone quarry. 

4 Reference to specific products does 
not imply endorsement by the Bureau of 
Mines. 




FIGURE 1. — Blackwell model 5, serial No. 2, visual task 
evaluator (VTE). 



target) with the Minolta meter (fig. 3). 
In addition, Munsell charts were used 
where needed to determine the reflectance 
of surfaces of interest (fig. 4). Slide 
photographs were also taken of the equip- 
ment and the detail of each task. 

VTE DESCRIPTION AND PRINCIPLE 
OF OPERATION 

The Blackwell model 5 VTE is the latest 
in a series of visibility meters devel- 
oped by H. Richard Blackwell (2) of Vi- 
sioneering Laboratories. The main advan- 
tage of the new meter is that it uses 
light from the task environment rather 
than an internal, diffuse, incandescent 




g^ IW m 







FIGURE 2.— Outer rectangular lens units of VTE. 





FIGURE 3. — Minolta 1° luminance meter and RS-1 reflectance standard. 



source. This makes 
for use in the surfa 
(3). 

The VTE operates 
to vary the visual 
seen through the ins 
the luminance of a 
same time introduci 
luminance, or "opti 



the VTE very flexible 
ce mining environment 

by allowing the user 
contrast of objects 

trument by fading out 
scene while at the 

ng a uniform veiling 

cal fog." The point 



at which critical detail of the task can 
be seen just barely through the interven- 
ing optical fog is called threshold. The 
proportion of the original contrast pass- 
ing through the instrument's optics is 
called the contrast transmittance (CT) of 
the instrument, which ranges from almost 
100% to almost zero as the backeround lu- 
minance remains nearlv constant (M« 




FIGURE 4.— Munsell charts, multicolored chips for judging reflectance. 



A measure of how easy or how well a 
given target can be seen is expressed in 
the amount of reduction in task contrast 
that is needed to bring the detail to 
threshold. If, for example, a given tar- 
get object reaches visibility threshold 
at a value of CT equal to 0.10, the tar- 
get is inherently 10 times above its 
threshold value. The target is said to 
have a relative visibility level (VL) of 
10. Thus, a measure of relative visi- 
bility for objects is determined mathe- 
matically by taking the reciprocal of 
the contrast transmittance; namely, VL 
= 1/CT. Consequently, scenes that are 
highly visible will require more contrast 
reduction (optical fog) to reach visibil- 
ity threshold, while those that are mod- 
erately visible will require less (4-5_ ) . 

CIE-IES METHOD 

The use of the VTE to obtain visibility 
measurements is based on the CIE-IES 



method, which compares an actual, real- 
world visual task with a standard visi- 
bility reference task. The visibility 
reference task consists of an observer 
viewing (through the VTE) a luminous disk 
whose diameter subtends A' of arc at the 
observer's eyes when it is presented in a 
series of 0.2-s exposures on a. task back- 
ground with uniform luminance. In turn, 
the visibility reference task is the ba- 
sis for the visibility reference func- 
tion, which represents visibility thresh- 
old values obtained by a 20- to 30-yr-old 
reference observer (6^). A detailed ex- 
planation of this method is contained in 
CIE Report 19/2 (7^. Further, measuring 
task visibility with the VTE requires 
that the VTE user go through a specific 
calibration procedure. This procedure, 
with the procedure for analyzing the 
field data, is included in appendix B at 
the end of this report. 



DISCUSSION AND RESULTS 



This section includes a brief descrip- 
tion of the different equipment studied, 
with corresponding tables of illumination 



data based on measurements of task visi- 
bility for equipment operators. The data 
presented should not be construed as 



absolute, but should be used as a general 
guide to help In better understanding the 
illumination needs of machinery and vehi- 
cle operators at surface mines. Also, 
note the following regarding data in the 
tables: 

Values appearing under the column head- 
ings "Computed luminance" and "Computed 
illuminance" were calculated for the me- 
dian age in each group, that is, the 
average 25- and 50-yr-olds of the normal 
population. 

Computed values of luminance and illu- 
minance were rounded off for consistency 
after the calculations were made. 

Variations in luminances and illumi- 
nances for similar tasks and equipment 
are largely the result of the wide dif- 
ferences in the conditions under which 
field measurements were actually taken. 

In general, high contrast between the 
task target or critical detail and its 
background will result in good visibility 
and relatively lower illuminance levels, 
while low contrast will result in poorer 
visibility and relatively higher levels 
of illuminance. 

The footnote "Supplemental lighting" on 
some of the tables refers to illumination 
added to the scene for certain visual 
tasks (generally from the direction of 
normal or existing lighting) to increase 
the transmittance through the VTE. 

SURFACE COAL MINES 

Draglines 

Draglines are generally very large, 
mobile, electric-powered excavating ma- 
chines used to remove and transport over- 
burden (the earth and rock overlying a 
coalbed) while operating from the top 
edge of a nearly vertical pit. Those 
working on or near a dragline include an 
operator, an oiler, and a groundman who 
usually operates a track- or wheel-type 
bulldozer to maintain a relatively uni- 
form ground surface around the dragline 
and handles the trailing cable for relo- 
cation purposes. For obvious safety rea- 
sons, good visibility is a necessary 



concern for tasks on and around the ma- 
chine. Accordingly, the dragline opera- 
tor must be able to see the following: 
the bottom of the pit at the greatest 
reach and digging depth of the machine, 
for positioning of the bucket; the point 
at which the overburden meets the coal, 
to remove only overburden; the top of the 
spoil pile or waste dump when disposing 
of overburden; and on the hoist rope, the 
bucket-chain assembly including the dump 
block, to prevent lifting the dump block 
into the point sheave located at the end 
of the boom. Other tasks for workers In- 
clude approaching, boarding, and exiting 
the machine, routine maintenance, and in- 
spection. A final task involves handling 
of the trailing cable during relocation 
maneuvers. 5 

The three draglines observed during 
field investigations displayed illumina- 
tion systems consisting of mercury vapor 
luminaires and some high-pressure sodium 
vapor luminaires; these were mounted on 
the boom and around the top edge of the 
machinery house. Incandescent fixtures 
were generally located near doorways, 
walkways, stairways, and ladders, and 
beneath the mainframe of the machine. 
Figure 5 shows an illuminated dragline 
operating at night. Table 1 shows tasks 
for which visibility was measured, along 
with the existing and computed illumina- 
tion and task viewing distances. 

In addition to the data in table 1, 
more comprehensive data on the illumina- 
tion needs for tasks on draglines can be 
found in a report by Crouch and Vincent. ^ 

^Some information contained in this 
paragraph was obtained from a "rough" 
draft report of the CIE Subcommittee SC- 
4.1 OB, entitled "Recommended Practices 
For Open Cast Mine Lighting," and com- 
pleted on Jan. 25, 1983. This report is 
yet to be published in its entirety and 
final .form. 

^This report documents work performed 
for the Mine Safety Appliance Co. under 
Bureau contract H03874024. A copy of the 
report is available upon request from 
A. G. Mayton, BuMines, Pittsburgh, PA. 




FIGURE 5. — Typical lighting on dragline operating during nighttime hours. 

TABLE 1. - Illumination values resulting from task visibility measurements 
for coal mine draglines 



Existing 
illumi- 


Viewing 

distance, 

ft 


Computed 
luminance, 
fL 1 ' 2 


Reflec- 
tance, 
% 


Computed 

illuminance, 

fc 1 ' 3 


nance, 
fc 


20- to 

30-yr- 

olds 


40- to 

60-yr- 

olds 


20- to 

30-yr- 

olds 


40- to 

60-yr- 

olds 




DRAGLINE 


1 











Seen from operator's 
















cab: Tooth of bucket 


















5.11 


100 


0.058 


0.095 


9.00 


3.10 


5.13 







DRAGLINE 


2 










Seen from operator's 
















cab: 


















4 2.40 


150 


0.036 


0.058 


2.08 


1.74 


2.80 


Lower edge of bucket 


















4 1.38 


105 


.371 


.743 


47.10 


.79 


1.58 


Coal with respect to 


















4 1.34 


150 


1.18 


2.99 


14.18 


8.34 


21.11 


Dump block on hoist 






4 2.10 


150 


.039 


.063 


2.86 


1.36 


2.19 


Seen from ground level 
















at rear of machine: 


















1.31 


3.7 


2.22 


6.86 


9.92 


22.40 


69.17 



DRAGLINE 3 



Seen from operator's 
















cab: 
















Control panel button. . 


9.24 


1.8 


0.037 


0.060 


34.52 


0.11 


0.17 


Tooth of bucket rest- 


















1.27 


241 


1.121 


2.193 


18.90 


5.94 


11.61 


Seen from landing: Edge 
















of landing to stairs... 


3.48 


4.7 


.014 


.022 


3.45 


.41 


.61 



Calculated for median age in each group. 

To convert to candelas per square meter, multiply by 3.426. 
3 To convert to lux, multiply by 10.76. 
Extrapolated from other measurements. 



Stripping and Loading Shovels 

The lighting of both stripping and 
loading shovels was observed and stud- 
ied, although task visibility measure- 
ments were obtained only for loading 
shovels. Personnel and visibility re- 
quirements are generally the same as 
those for draglines. 

Stripping shovels (fig. 6) work in the 
pit on top of the coalbed and move along 
the pit by crawler-type conveyance. Like 
draglines, they remove a highwall of 
overburden (up to 100 ft or more) and de- 
posit it on a spoil pile at a distance of 
the boom's length away. The visibility 
requirements of the shovel operator and 
the groundman differ from those of work- 
ers on the dragline in that a dominant 
safety concern is the highwall, which 
must be monitored continually for dangers 
due to material falling or rolling down 
the face of the highwall. 

Loading shovels (fig. 7) operate on the 
bottom of a bench of broken overburden or 



coal. Bench heights typically range from 
15 to 40 ft. The operating characteris- 
tics of this type of shovel are the same 
as those of the stripping shovel, except 
that the stripping shovel transports the 
overburden to a spoil pile, while the 
loading shovel loads overburden or coal 
into trucks that transport it to a desig- 
nated dump area or hopper. 

Visual tasks were identified and vis- 
ibility was measured for five loading 
shovels. Illumination of these shovels, 
like that of the draglines, was provided 
by a combination of primarily mercury va- 
por luminaires with high-pressure sodium 
and incandescent luminaires. Visual 
tasks for these machines, with computed 
values of illumination, are shown in ta- 
ble 2. Additional information on the il- 
lumination needs for tasks on electric- 
powered shovels can also be found in 
Crouch and Vincent. 

'See footnote 6. 




FIGURE 6.— Stripping shovel with typical lighting system. 



TABLE 2. - Illumination values resulting from task visibility measurements 
for coal mine shovels 



Existing 
illumi- 
nance, 
fc 



Viewing 
distance, 
ft 



Computed 
luminance, 
fL 1 ' 2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 
% 



Computed 

illuminance, 

fc 1 ' 3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



SHOVEL 1 



Seen from operator's 
cab: Rear edge of 
dipper resting on 
ground . 



6.84 



28 



0.381 0.765 



16.52 



2.31 4.63 







SHOVEL 


2 










Seen from operator's 
cab: 
Rear edge of 


1.41 

.70 

2.00 


50 
25 
24.6 


0.038 
.251 
.080 


■ 

0.061 
.478 
.139 


4.26 
10.00 
10.00 


0.89 

2.52 

.80 


1.43 


Rock on slope of 

Rear edge of dipper 
resting on ground. . 


4.78 
1.39 







SHOVEL 


3 










Seen from operator's 
















cab: 
















Top rear edge of 


4 1.40 


30 


0.240 


0.453 


10.00 


2.40 


4.53 


Top edge of empty 
Top edge of truck 


4 1.20 
4 1.30 
4 1.70 


20 
25 
30 


.062 
.513 
.045 


.103 
1.08 
.074 


10.00 

34.62 

1.76 


.62 

1.48 
2.58 


1.03 
3.12 


Height of load in 


4.20 


Seen from ground level 




at rear of machine: 


.23 


3.5 


.020 


.031 


17.39 


.12 


.63 



SHOVEL 4 



Seen from operator's 
cab: Top rear edge 
of loaded dipper. . . . 



12.60 



25 



1.30 



3.39 



10.00 



13.06 



33.91 







SHOVEL 


5 










Seen from ground level 
















at rear of machine: 
















Bottom rung of 
















boarding ladder.... 


2.09 


2.3 


0.140 


0.248 


12.92 


1.08 


1.92 


5th rung of boarding 
















ladder used as 


















2.83 


1.3 


.003 


.005 


.71 


.46 


.66 


Toi...i.» n j e~— _.ji._ 


. 















Calculated for median age in each group. 
To convert to candelas per square meter, multiply by 3.426. 
3 To convert to lux, multiply by 10.76. 
Extrapolated from other measurements. 



10 




FIGURE 7. — Typical illumination on loading shovel. 




FIGURE 8.— Typical lighting system on loader. 



11 



TABLE 3. - Illumination values resulting from task visibility measurements 
for coal mine loaders 





Existing 
illumi- 
nance, 
fc 


Viewing 
distance, 
ft 


Computed 
luminance, 
fL 1 ' 2 


Reflec- 
tance, 
% 


Computed 

illuminance, 

fc 1 ' 3 




20- to 

30-yr- 

olds 


40- to 

60-yr- 

olds 


20- to 

30-yr- 

olds 


40- to 

60-yr- 

olds 






LOADER 


1 










Seen from ground level 
at boarding ladder: 


4 0.78 
4 .02 

1.01 
.39 

.37 


2.3 

1.4 

1.4 
3.6 

15 


0.017 
.016 

.017 
.068 

.031 


0.026 
.024 

.026 
.114 

.050 


1.28 
50.00 

1.98 
10.26 

10.81 


1.33 
.03 

.86 
.66 

.29 


2.06 




.05 


Seen from plate-metal 
landing outside oper- 
ator's cab: 


1.33 


Edge of landing to 

Seen from operator's 
cab: Height of load 


1.11 
.46 






LOADER 


2 










Seen from operator's 
cab: Left end of 


2.65 


15 


0.028 


0.046 


1.89 


1.51 


2.41 






LOADER 


3 










Seen from operator's 
cab: Top rear edge 


8.78 


13 


0.162 


0.294 


17.08 


0.95 


1.72 



Calculated for median age in each 

To convert to candelas per square 

3 To convert to lux, multiply by 10, 

Supplemental lighting required to 



group. 

meter, multiply by 3.426. 

76. 

make measurements. 



Loaders 



A wheel-tractor loader is a very common 
machine around a surface mining pit. It 
can be used in a number of ways at a min- 
ing operation, but its most important 
function is to remove overburden or coal 
and load it into trucks or railroad cars 
for transport to a designated dump area. 

Loader operators must have good visi- 
bility to board and exit the equipment 
via boarding ladders and cab decks or 
landings. The operators must be able to 
see the immediate areas adjacent to ei- 
ther end of the bucket, determine when 
the bucket is full, detect any loose or 
falling material when near the highwall, 



determine the position of the truck or 
railroad car to be loaded with respect to 
the loader bucket, and see other moving 
vehicles and hazards when traveling from 
one location to another within the mine. 

Illumination systems on loaders usual- 
ly consist of regular incandescent or, in 
some cases, quartz halogen luminaires. 
Figure 8 shows the lighting system on a 
typical loader. Table 3 shows existing 
and computed illumination values for var- 
ious tasks of loader operators. 

Haul Trucks 



There are basically two types of haul- 
age trucks used at surface coal mines: 



12 



the rear dump, used primarily for trans- 
porting overburden, and the center (bot- 
tom) dump, used for transporting coal. 
Illumination of haul trucks consists typ- 
ically of high- and low-beam headlights 
and a set of rear-mounted backup lights 
(on rear dumps only). In some instances, 
mine operators have mounted an additional 
floodlight behind the cab of rear-dump 
trucks for dumping purposes. The visi- 
bility required by truck drivers includes 
the following: seeing the ladders and 
handrails when boarding and exiting the 
truck, viewing the area near the shovel 
or loader at a loading site, viewing the 
berm or edge of the dump and general area 
of the dumping site, and readily detect- 
ing hazards and other moving equipment on 
haulage roads when driving from place to 
place within the mine. Driver visibility 
was measured for various tasks on five 
haul trucks. These tasks are shown in 
table 4 with the existing and computed 
levels of illumination. Figure 9 shows a 
typical rear-dump haul truck at a dump 
site. 



Blasthole Drills 

Rotary blasthole drills are an impor- 
tant facet of the overburden removal pro- 
cess. Drills are used to bore vertical 
or angled holes into the overburden. The 
holes are then filled with explosives and 
detonated to break up the overburden into 
fragments that can easily be removed by 
the excavating equipment. The illumina- 
tion of drills includes mercury vapor 
luminaires that are mounted on the top of 
the operator's cab to illuminate the mast 
and the drill table or deck through which 
the drill pipe passes down to the hole. 
Some drills are also equipped with high- 
pressure sodium vapor luminaires at the 
rear and sides of the machines and incan- 
descent fixtures to illuminate doorways 
to the house, the main walkway, and the 
boarding stairs or ladders. Figure 10 
shows the typical illumination on a drill. 

In most cases, two people work on a 
drill, an operator and an oiler. The 
visibility required for these workers 
includes the ability to see the area 




FIGURE 9. — Haul truck dumping load at waste dump. 



13 



TABLE 4. - Illumination values resulting from task visibility measurements 
for coal mine haul trucks 



Existing 

i 1 lumi - 

nance, 

fc 



Viewing 
distance, 
ft 



Computed 
luminance, 

flJ.2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 
% 



Computed 

illuminance, 

fc 1 ' 3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 







TRUCK 


1 










Seen from driver's 
















cab: 
Pile of debris in 


0.50 
.54 


130 
55 


0.107 
.018 


0.186 
.029 


14.81 
1.85 


0.72 
1.00 


1.25 
1.55 


Seen from ground level 
at boarding ladder: 


4 1.21 
4 .61 


2.2 

1.3 


.018 
.043 


.028 
.070 


1.65 
8.20 


1.10 
.53 


1.71 




.85 



TRUCK 2 



Seen from driver's 
















cab: Left curb at 


















1.02 


35 


0.620 


1.37 


6.86 


9.04 


19.97 



TRUCK 3 



Seen from driver's 
















cab: 
















Edge of berm at 


















0.91 


32.5 


0.025 


0.041 


1.10 


2.27 


3.71 


Body-down indicator. 


4 .31 


3 


.069 


.115 


6.45 


1.08 


1.78 







TRUCK 


4 










Landing at head of 
boarding ladder: 
Handrail of landing. 
Edge of landing 


0.10 
.54 


1.8 
3.6 


0.022 
.016 


0.035 
.026 


20.00 
1.80 


0.11 
.89 


0.18 
1.45 



TRUCK 5 



Seen from driver's 
cab: 5 
Tire track at load- 
ing shovel 6 

Sloped waste pile at 
base of bench 

highwall 6 

Rear (shadowed) edge 
of loading shovel 6 . 



3.15 

1.48 
1.90 



99.3 

138 
99.3 



0.432 

.198 
.781 



0.886 

.367 
1.78 



8.89 

1.35 
10.00 



4.86 

14.67 
7.81 



9.97 

27.18 
17.80 



Calculated for median age in each group. 

To convert to candelas per square meter, multiply by 3.426. 

To convert to lux, multiply by 10.76. 

Supplemental lighting required to make measurements. 

Left side-view mirror used. 

Positioning and/or maneuvering mark. 



14 




FIGURE 10.— Typical illumination on blast hole drill. 



around the drill for different operating 
maneuvers; walkways, stairs, and ladders 
for boarding and exiting; and -areas imme- 
diately adjacent to the operator's and 
rear sides of the machine to relocate the 
machine for drilling the next hole. The 
visibility for various tasks was measured 
on six blasthole drills; the tasks are 
shown in table 5 with corresponding illu- 
mination levels. 

Explosives Trucks 

Explosives trucks (figs. 11-12) are 
used for transporting a bulk explosive 
mixture or packaged explosives to the lo- 
cation of previously drilled blastholes. 
Here the driver of the truck loads the 
blastholes with the explosives and pre- 
pares the holes for firing during the 
next day shift. General visibility re- 
quirements include being able to see the 
general area around the drilled holes, 
steps and handles for entering or exiting 



the truck, and hazards or other vehicles 
while traveling from one location to 
another in the mine. Specific tasks and 
corresponding light levels for two explo- 
sives trucks are shown in table 6. 

Scrapers 

Wheel-tractor scrapers are another type 
of excavating equipment used in surface 
coal mines. They are used primarily for 
removing and transporting topsoil or very 
shallow overburden. Illumination, like 
that on haulage trucks, is primarily ac- 
complished with headlights that have the 
high- and low-beam feature. If the ma- 
chine design permits, mine operators will 
sometimes add incandescent floodlights to 
better illuminate the area to the front 
of a scraper. One other incandescent lu- 
minaire is mounted on the rear of the 
driver's cab to provide illumination for 
the pan. Figure 13 shows a typical 
scraper with incandescent lighting. 



15 



TABLE 5. - Illumination values resulting from task visibility measurements 
for coal mine blasthole drills 



Existing 
illumi- 
nance, 
fc 



Viewing 

distance, 

ft 



Computed 
luminance, 
fL 1 ' 2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 

% 



Computed 

illuminance, 

fc 1 ' 3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



DRILL 1 



Seen from operator's cab: 
Shovel (marker) to align 
machine for drilling 


27.24 

15.10 
16.53 


60 

8 

12 


0.226 

.128 

.081 


0.423 

.227 
.137 


16.52 

4.44 
15.12 


1.37 

2.89 

.54 


2.56 


Stem lock against drill 


5. 11 


Paint mark on hoist chain 


.91 



DRILL 2 



Seen from landing at head 
of boarding ladder: Edge 
of landing to descend 
stairs 



2.40 



3.7 



0.063 



0.106 



4.17 



1.52 



2.55 



DRILL 3 



Seen in operator's cab: 
Pointer of pressure gauge. 



1.51 



1.5 



0.012 



0.018 



56.95 



0.02 



0.03 







DRILL 4 












Seen from operator's cab: 
















Edge of box (marker) to 
















align machine for drill- 


















1.43 


21 


0.568 


1.22 


6.99 


8.12 


17.45 


Edge of deck bushing 


















9.18 


4.5 


.533 


1.13 


5.45 


9.78 


20.71 


Rope with weighted end 


















4 23.30 


20 


.336 


.663 


4.25 


7.91 


15.61 


Seen from ground level at 
















operator's cab: Boarding 


















2.16 


4.5 


.028 


.045 


4.63 


.60 


.96 



DRILL 5 



Seen from operator's cab: 
Edge of deck bushing 

without drill pipe 

Edge of pipe rack against 

drill pipe 

Seen from ground level at 
boarding stairs: 

Bottom step 

Handrail 



2.14 
4.43 



4.50 
1.31 



2.1 
1.8 



0.147 
.091 



.032 
.095 



,262 
,156 



,0T1 
,163 



2.34 
10.38 



8.22 
8.40 



6.27 
.88 



.38 
1.13 



11.21 
1.50 



.62 
1.94 



DRILL 6 



Seen from operator's cab: 
















Edge of deck bushing 


















1.48 


5 


0.304 


0.588 


25.00 


1.22 


2.35 




.93 


4.3 


.029 


.041 


13.98 


.65 


1.00 


Drop pin in drill pipe 


















55 


6 


.790 


1.81 


21.82 


3.62 


8.30 


Pointer of pressure gauge 


6 


1.4 


.616 


1.35 


62.17 


.99 


2.17 




2.85 


4 


.458 


.948 


32.28 


1.42 


2.94 



Calculated for median age in each groupc 

To convert to candelas per square meter, multiply by 3.426. 

To convert to lux, multiply by 10.76. 

Supplemental lighting required to make measurements. 



16 




FIGURE 11. — Flatbed truck for transporting packaged explosives. 




■■llillilll WMilH li ii il iHWhrtliiHP 

FIGURE 12.— Tank- or drum-type truck for transporting bulk mixture of explosives. 



17 



Visibility required by scraper opera- 
tors includes the ability to see hazards 
or other moving vehicles while moving 
from one location to another, the mate- 
rial to be loaded and the general area 
where loading takes place, the cutting 
edge of the pan to begin loading, the 



material level in the pan when filled, 
and the general area where loaded mate- 
rial is being deposited. Visibility was 
measured for a number of tasks on two 
scrapers. Table 7 shows the tasks and 
task viewing distances with existing and 
computed illumination levels. 



TABLE 6. - Illumination values resulting from task visibility measurements 
for coal mine explosives trucks 



Existing 
illumi- 
nance, 
fc 



Viewing 
distance, 
ft 



Computed 
luminance, 
fL 1 ' 2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 
% 



Computed 
illuminance, 

fc 1 ' 3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 







TRUCK 


1 










Seen from ground level 
















at rear of truck: 
















Edge of bagged 


















1.84 


3 


1.04 


2.53 


29.35 


3.54 


8.64 


Detonating cord 






2.30 


1.3 


.188 


.347 


27.83 


.68 


1.25 


Hole slot in primer. 


2.28 


1.3 


.258 


.493 


32.46 


.79 


1.52 


Black digit on tape 


















20.70 


4.3 


.718 


1.62 


9.90 


7.25 


16.37 



TRUCK 2 



Seen from ground level 
















at rear of truck: 
















Edge of blasthole. . . . 


4 150 


4.5 


0.312 


0.612 


9.93 


3.14 


6.16 



Calculated for median age in each group. 

To convert to candelas per square meter, multiply by 3.426, 

To convert to lux, multiply by 10.76. 

Supplemental lighting required to make measurements. 




FIGURE 13.— Typical lighting on scraper. 



18 



TABLE 7. - Illumination values resulting from task visibility measurements 
for coal mine scrapers 



Calculated for median age in each group. 

"To convert to candelas per square meter, multiply by 3.426. 
To convert to lux, multiply by 10.76. 
Extrapolated from other measurements. 
'Supplemental lighting required to make measurements. 









Computed 




Computed 




Existing 


Viewing 


luminance, 


Reflec- 


illumi 


nance , 




illumi- 
nance, 


distance, 
ft 


fL 1 


,2 


tance, 

% 


fc 1 


,3 




20- to 


40- to 


20- to 


40- to 




fc 




30-yr- 


60-yr- 




30-yr- 


60-yr- 








olds 


olds 




olds 


olds 


SCRAPER 1 


Seen from operator's 
















cab: 
















Cutting edge of pan. 


1.96 


16 


2.15 


6.49 


18.88 


11.40 


34.39 




.77 


39.6 


.635 


1.40 


20.78 


3.06 


6.74 




.45 


47 


1.47 


3.97 


17.78 


8.26 


22.32 


Top rear edge of 


















4 8.20 


14 


.204 


.378 


9.76 


2.09 


3.87 


Seen from ground level 
















at rear push bumper: 


















5 12.24 


2 


.012 


.019 


2.53 


.49 


.76 


Hand bar for 


















5 1.79 


1.3 


.776 


1.79 


14.52 


5.34 


12.30 






SCRAPE 


R 2 










Seen from operator's 
















cab: Cutting edge of 


















54.0 


19 


0.028 


0.046 


12.52 


0.23 


0.36 



Bulldozers 



Graders 



Track- or wheel-type tractors or simply 
dozers are indispensable items of equip- 
ment for surface mine operators, because 
of the power they possess to push or pull 
other machines, objects, etc. Although 
they can be used in many ways, their main 
function is to redistribute overburden at 
dump sites and at dragline and shovel 
working areas. The illumination system 
of a typical dozer generally consists of 
incandescent floodlight luminaires that 
are mounted in the front and rear, and in 
some cases, on top of the operator's cab. 
A track dozer with Incandescent lighting 
is shown in figure 14. 

Table 8 shows the results of task visi- 
bility and illumination measurements for 
11 dozers. 



Motor graders are used to maintain haul 
roads leading to dump areas and access 
roads in and around the pit area. Illu- 
mination systems are similar to those of 
loaders and dozers, in that they are 
mainly incandescent floodlights mounted 
on the front and rear of the machine and 
on the top of the operator's cab. An ex- 
ample of a motor grader with an incandes- 
cent lighting system is shown in figure 
15. General visibility requirements for 
the grader operator include the ability 
to see obstacles, hazards, and other ve- 
hicles when traveling throughout the 
mine; the areas adjacent to either end of 
the blade; the wind row of material being 
pushed; and the ladder-type steps and 
hand bars needed for boarding and getting 



19 



TABLE 8. - Illumination values resulting from task visibility measurements 
for coal mine bulldozers 



Existing 
illumi- 
nance, 
fc 



Viewing 

distance, 

ft 



Computed 
luminance, 
fL 1 ' 2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 
% 



Computed 

illuminance, 

fc 1 ' 3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



BULLDOZER 1 



Seen from operator's 
cab: 
Dirt at left blade 
end 

Dirt above blade 
when pushing load. 



0.80 
135.70 



23 
16 



0.054 
.002 



0.088 
.003 



1.25 
.02 



4.32 
10.00 



7.05 
15.00 



BULLDOZER 2 



Seen from operator's 
cab: Dirt at right 

blade end 

Seen from ground 
level: 
Hand bar above 
trunnion arm for 

boarding 

Edge of trunnion arm 
step for boarding.. 



1.56 



.41 
.44 



20 



1.6 
1.6 



0.063 



2.96 
.021 



0.014 



10.27 
.033 



1.92 



34.15 
4.54 



3.26 



8.65 
.46 



5.43 



30.09 
.72 



BULLDOZER 3 



Seen from operator's 
cab: Power cable of 
dragline 



0.47 



42.2 0.492 1.03 21.28 



5.25 



11.00 







BULLDOZER 4 










Seen from ground 
level: 
Edge of bottom rung 
of boarding ladder. 


0.06 
.03 


2.1 
1.4 


0.018 
.086 


0.028 
.146 


16.67 
100.0 


0.11 
.09 


0.17 
.15 


Seen from operator's 
cab: Top edge of 
blade against load 


42.65 


14 


.421 


.864 


4.99 


8.43 


17.30 



BULLDOZER 5 



Seen from operator's 
cab: Left blade end 
against load pushed. « 



0.86 



15 



0.325 



0.637 



30.23 



1.08 



2.11 



BULLDOZER 6 



Seen from operator's 
cab: Left blade end 
against load pushed. « 



4 122.40 



15.6 0.085 



0.145 



3.34 



2.54 



4.34 



BULLDOZER 7 



Seen from operator's 






■ - ■ - — ■ ■ ■ ■■ 1 










cab: Left blade end 
















against load pushed.. 


4 12.60 


15.3 


0.188 


0.344 


23.81 


0.79 


1.45 



See footnotes at end of table. 



20 



TABLE 8. - Illumination values resulting from task visibility measurements 
for coal mine bulldozers — Continued 



Existing 
illumi- 
nance, 
fc 



Viewing 
distance, 
ft 



Computed 
luminance, 
fL 1 ' 2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 

% 



Computed 

illuminance, 

fc 1 ' 3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 
olds 



BULLDOZER 8 



Seen from ground level 
at rear of machine: 
Edge of grouzer 
(step) for boarding. . 



4 42.20 



2.1 0.001 0.002 



0.02 



5.00 



10.00 



BULLDOZER 9 



Seen from operator's 
cab: Left blade end 
against muddy load 
pushed 



1.51 



17.5 0.035 0.056 



4.64 



0.76 



1.20 







BULLDOZER 10 










Seen from operator's 
















cab: Top of blade 
















against load pushed. . 


6.35 


13.3 


0.132 


0.234 


8.66 


1.52 


2.70 


Seen from ground level 
















at boarding ladder: 


















4 36.80 


2.5 


.008 


.012 


.46 


1.78 


2.57 




1.32 


1.3 


.057 


.093 


61.36 


.09 


.15 



BULLDOZER 11 



Seen from operator's 
cab: 
Left blade end 
















against ground 


1.39 

3.26 
1.33 


14.8 

14.5 
3.3 


0.572 

.081 
.200 


1.23 

.138 
.368 


17.27 

8.28 
32.33 


3.31 

.98 
.62 


7.12 


Top right blade end 
against ground 


1.67 


Edge of deck outside 

Seen from ground 
level: 


1.14 


Edge of trunnion arm 
(step) for boarding 
Hand bar above 


.39 


1.7 


.010 


.015 


2.56 


.39 


.60 


trunnion arm for 


.93 


2.8 


.005 


.007 


2.15 


.23 


.35 






v, ~—~..._ 













To convert to candelas per square 
To convert to lux, multiply by 10 
Supplemental lighting required to 



group. 

meter, multiply by 3.426. 

76. 

make measurements. 



21 




FIGURE 14.— Typical lighting on bulldozer. 



• 




^ ^ 






■■ -■■-■. 






BHi^,7^^^BB 




L 


*w 


i ^Jz 




I 


I 

i 


■1 ■■**■. 








■ j tl ^< • ... 




,.,'. . ' PWI "™^^^^^W^" II '■ill IIP.'I! UIWIH'lHil II I'll 




^s, -. W**** - 


ii|8i^itir;^ M ^ fe6t ~ J '"'- 









FIGURE 15.— Typical illumination system on motor grader. 



off the machine. Table 9 shows the illu- 
mination levels with corresponding tasks 
for four motor graders. 

Service Vehicles 

Various types of service vehicles are 
an essential part of coal mining pit 



operations. Fuel and lubrication trucks 
(figs. 16-17), which may work in pairs, 
are used to maintain equipment in the pit 
area. As their names imply, they are 
used in replenishing diesel fuel, greas- 
ing appropriate parts, and checking and 
replacing various filters on mobile die- 
sel equipment. 



22 



TABLE 9. - Illumination values resulting from task visibility measurements 
for coal mine motor graders 









Computed 




Computed 




Existing 


Viewing 


luminance, 


Reflec- 


illumi 


nance, 




illumi- 
nance, 


distance, 
ft 


fL 


,2 


tance, 

% 


fc 1 


,3 




20- to 


40- to 


20- to 


40- to 




fc 




30-yr- 


60-yr- 




30-yr- 


60-yr- 








olds 


olds 




olds 


olds 






GRADER 


1 










Seen from operator's 
















cab: 


















4 0.31 


85 


2.57 


8.43 


29.03 


8.84 


29.05 


Top of wind row at 
















right blade end.... 


1.04 


14.6 


.106 


.184 


4.81 


2.20 


3.82 


Top of left blade 


















6.26 
.44 


10.7 
65 


.014 
.492 


.021 
1.03 


.96 
22.73 


1.46 
2.16 


2. 16 




4.53 


Clumped dirt at 
















right blade end.... 


1.35 


14.7 


5.41 


25.76 


28.15 


19.20 


91.51 


Seen from ground level 
















at boarding ladder: 


















4 .63 


1.9 


.024 


.037 


4.76 


.50 


.78 




4 .11 


1.4 


.009 


.014 


9.09 


.10 


.15 







GRADER 


2 










Seen from operator's 
















cab: 


















5.63 


13.4 


0.014 


0.021 


1.06 


1.30 


2.02 




7.23 


9.4 


.123 


.216 


14.38 


.86 


1.50 


Seen from ground level 
















at boarding ladder: 


















2.74 


1.9 


.320 


.625 


5.84 


5.48 


10.70 







GRADER 


. 3 










Seen from operator's 
cab: 

Bottom of left blade 


2.99 
1.23 
1.23 

.36 


13.3 
8.7 
7.8 

2 


0.008 
.007 
.027 

.041 


0.012 
.010 
.043 

.067 


0.67 

.81 

7.32 

22.22 


1.14 
.87 
.37 

.18 


1.76 
1.23 


Top of left blade 


.58 


Seen from ground level 
at boarding ladder: 


.30 



GRADER 4 



Seen from operator's 
















cab: 


















2.26 


9 


0.012 


0.019 


1.33 


0.94 


1.45 




2.45 


13.4 


.080 


.135 


5.31 


1.50 


2.54 


Seen from ground level 
















at boarding ladder: 


















1.67 


1.7 


.052 


.085 


4.19 


1.23 


2.02 



Calculated for median age in each 
"To convert to candelas per square 
To convert to lux, multiply by 10. 
Supplemental lighting required to 



group. 

meter, multiply by 3.426. 

76. 

make measurements. 



23 




FIGURE 16. — Truck used for refueling and lubricating equipment. 




FIGURE 17. — Luminaires mounted on top rear section of lubrication truck. 



Illumination for these vehicles is sup- 
plied by incandescent luminaires mounted 
on the truck or handheld lamps or cap 
lamps. In some cases, quartz halogen lu- 
minaires are used. Also, these vehicles 
rely a great deal on the illumination 
systems of the equipment which they ser- 
vice for the lighting needed to do their 
work. 

General visibility requirements for op- 
erators of these vehicles are basically 
the same as those for operators of other 
mobile mining equipment. Tasks involve 
detecting hazards or other vehicles while 
driving to and from different working 



areas within the mine and seeing hand- 
holds, handles, and steps when getting in 
and out of the service vehicles or on and 
off equipment being serviced. Selected 
tasks for two fuel trucks and three lu- 
brication trucks are shown in tables 10 
and 11 with corresponding illumination 
levels for each task. 

Another type of service vehicle is the 
water truck, which is used to sprinkle or 
spray water onto haulage and access roads 
to allay dust. The primary illumination 
for watering vehicles, as for some of the 
vehicles previously mentioned, is the 
standard high- and low-beam headlights. 



24 



TABLE 10. - Illumination values resulting from task visibility measurements 
for coal mine fuel trucks 



Existing 
illumi- 
nance, 
fc 4 



Viewing 

distance, 

ft 



Computed 
luminance, 
fL 1 - 2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 
% 



Computed 

illuminance, 

fc 1 ' 3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



TRUCK 1 



Seen from ground 
level: 
Black digit of fuel 

meter 

Boarding step of cab 
Hand bar for 

boarding 

Seen from corner of 
walkway behind driv- 
er's cab: Edge of 
walkway along fuel 
t ank 



0.58 
.30 

1.65 



.24 



2.3 
2.7 

1.3 



4.6 



0.109 
.038 

.026 



.007 



0.190 
.061 

.041 



.010 



8.62 
13.33 

6.67 



4.17 



1.27 
.29 

.39 



.17 



2.20 
.46 

.62 



.25 







TRUCK 


. 2 










Seen from ground 
level: 
Black digit of fuel 


0.70 
1.02 
1.03 


1.3 
1.5 
3 


0.178 
.167 
.010 


0.325 
.304 
.015 


7.03 

17.65 

.97 


2.54 

.95 

1.03 


4.63 


Nozzle of fuel hose. 
Boarding step of cab 


1.72 
1.59 



Calculated for median 



2 To convert to candelas 
To convert to lux, mul 
Supplemental lighting 



age in each group. 

per square meter, multiply by 3.426. 
tiply by 10.76. 
required to make measurements. 



In many cases, water trucks are modified 
forms of other equipment, such as bottom- 
dump haul trucks or scrapers. In gen- 
eral, visibility is needed for many of 
the same types of tasks as required for 
the above vehicles. Selected tasks for 
one water truck are shown in table 12 
with corresponding existing and computed 
illumination levels. 

SURFACE METAL AND N0NMETAL MINES 

Surface methods are used to mine a num- 
ber of M-NM ores besides coal. The types 
of mines visited during this program in- 
cluded iron ore, phosphate, limestone, 
and granite quarries. With a few excep- 
tions, most of these mines are operated 
in much the same way as the surface coal 



mines with similar equipment and visibil- 
ity requirements for machinery operators. 

The two iron ore mines are large, open 
pit mines. The ore is mined by the 
benching method using loading shovels and 
haul trucks, which transport the ore to a 
primary crusher. From there it is con- 
veyed by belt to a secondary crusher and 
then processed into pellets at a plant 
located adjacent to the mining pit. 

The five phosphate mines employ drag- 
lines for excavating this very soft non- 
metallic ore. The draglines, which are 
essentially the only type of mobile 
equipment in operation during nighttime 
hours, dump the phosphate ore into small 
pits equipped with high-pressure water 
guns, which in turn wash the phosphate 
down into a "well." The slurry formed is 



25 



TABLE 11. - Illumination values resulting from task visibility measurements 
for coal mine lubrication trucks 



Existing 
illumi- 
nance, 



Viewing 

distance, 

ft 



Computed 
luminance, 
fL 1 ' 2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 
% 



Computed 

illuminance, 
fc 1,3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 







TRUCK 


1 










Seen from ground level 
at rear of truck: 

Nozzle of grease hose. 
Chain link of boarding 


1.21 
12.80 

358 


1.3 
2 

3.5 


0.054 
.029 

.064 


0.089 
.046 

.108 


9.09 
9.22 

.22 


0.59 
.32 

29.32 


0.98 
.50 

49.02 



TRUCK 2 



Seen from ground level 
















at grease fitting of 
















haul truck wheel: Noz- 


















314 


2.1 


0.040 


0.064 


6.30 


0.63 


1.02 







TRUCK 


3 










Seen from ground level: 
















Nozzle of grease hose. 


33.2 


1.6 


0.068 


0.114 


3.46 


1.96 


3.28 


Boarding step of cab. . 


1.19 


2 


.022 


.035 


9.24 


.24 


.38 


Hand bar for boarding. 


1.63 


1.5 


.004 


.006 


3.07 


.13 


.19 


i 


_ 4. _~~V 















„ _ _„ , 

To convert to candelas per square 
To convert to lux, multiply by 10 
Supplemental lighting required to 



group. 

meter, multiply by 3.426. 
,76. 
make measurements. 



TABLE 12. - Illumination values resulting from task visibility measurements 
for coal mine water truck 



Existing 
illumi- 
nance, 
fc 



Viewing 
distance, 
ft 



Computed 
luminance, 
fL'» 2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 



Computed 

illuminance, 

fc'' 3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Seen from operator's 
cab: 
Vertical stream of wa- 
ter at fillup point.. 
Top of berm at right 

side of road 

Water-filled pothole.. 

Rock on road 

Seen from ground level 
at boarding ladder: 

Bottom rung 

Handhold (rung) 



0.94 



117 



.69 


88 


1.13 


110 


.64 


110 


4 2.04 


2.5 


4 1.81 


1.3 



0.103 

.009 
.104 
.103 



,016 
.181 



0.177 

.013 
.181 
.177 



.025 
.330 



5.32 

1.45 
5.31 
7.81 



.98 
11.05 



Calculated for median age in each 
To convert to candelas per square 
To convert to lux, multiply by 10. 
Supplemental lighting required to 



group. 

meter, multiply by 3.426. 

76. 

make measurements. 



1.93 

.61 
1.97 
1.31 



1.66 
1.64 



3.33 

.92 
3.40 
2.27 



2.57 
2.98 



26 



then pumped through a pipeline to flota- 
tion plants where the sand is separated 
from the phosphate. Investigations at 
these mines did not include measurements 
of task visibility. 

The six limestone and calcite quarries 
operate with equipment such as loading 
shovels, loaders, haul trucks, and unit 
trains. Task visibility measurements at 
two of these mines are not included in 
the report because the VTE was later 
found to be out of calibration. Circum- 
stances did not permit measuring task 
visibility at one other of the quarries. 

The two granite quarries are rather 
unique compared with the types and meth- 
ods of mining previously discussed. The 
prominent item of equipment is the wire 
saw, which is used to cut huge slabs of 
granite from a massive face or wall. The 
saw consists of helical-shaped steel 
"wires," roughly 9/32 in. in diameter, 
which are strung over large sheaves re- 
sembling bicycle wheels. The sheaves are 
mounted on steel tower-like carriages lo- 
cated in channels cut out of either end 
of the working face. The wire of the saw 
is one continuous length, up to nearly 1 
mile strung around and across the quarry 
pit, and back and forth across the face 
to provide for as many as ten 1—1/2 — f t 
cuts. The wires, propelled at speeds up 
to 45 mph, are used to transport a water 



slurry consisting of silicon carbide 
granules fed into the cut from secondary 
reservoirs on the top of the face. The 
carbide granules ate the "blade" that ac- 
tually cuts the stone. Once the cut is 
made to the bottom of the quarry floor, 
the giant slab of granite (as large as 
125 by 1.5 by 100 ft) is broken into 
smaller size slabs or blocks with drills, 
jackhammers, regular hammers, shims, and 
wedges. The slabs are hoisted with 
cranes and placed on flatbed railroad 
cars that transport them to a cutting and 
finishing plant located at or very near 
the quarry. 

The wire saw is the focus of work ac- 
tivity during nighttime hours. Visibil- 
ity requirements include the inspection 
of: wires and sheaves at carriages, 
slurry pumps (at the bottom of each chan- 
nel) and slurry reservoirs (main and sec- 
ondary), and the general area on top of 
the granite face. Data on task visibil- 
ity were obtained but not included in the 
report because the VTE was later found to 
be out of calibration. 

Tables 13, 14, and 15 summarize the 
measurements of task visibility at sev- 
eral of the above M-NM mines. These ta- 
bles show various visual tasks with ex- 
isting and computed illumination levels 
for shovels, blasthole drills, and load- 
ers, respectively. 



CONCLUSIONS AND RECOMMENDATIONS 



This study shows that the type and ex- 
tent of illumination varies from mine to 
mine and seems to be influenced by sev- 
eral factors including mine size, ton- 
nage, and management philosophy. Al- 
though operators of surface mines and 
quarries have generally made positive 
strides toward providing adequate machine 
lighting, the results of the study in- 
dicate there are some instances where 
higher levels of illumination are re- 
quired than are available. The lighting 
and/or visibility for the visual tasks of 
machinery operators could be improved 
in several specific working areas on or 
about equipment including, among others, 
draglines, shovels, dozers, loaders, and 
haul trucks. Some examples and suggested 
improvements are as follows: 



1. The power cable on draglines or 
shovels must be handled when relocating 
these machines. Because the cable is 
frequently dragged along the ground dur- 
ing these procedures, it can become dis- 
colored so that it blends with the sur- 
face of the ground. In a previous study, 
Crouch and Vincent 8 reported that by in- 
creasing the contrast of the task detail 
as seen against its background, the visi- 
bility of a task can be increased, re- 
sulting in lower illumination require- 
ments. The visibility of the power cable 
in this case could be improved by apply- 
ing material such as reflective tape, to 
increase the cable's contrast as seen 
against its background, the ground 
surface. 

°See footnote 6. 



27 



TABLE 13. - Illumination values resulting from task visibility measurements 
for noncoal mine shovels 



Existing 
illumi- 
nance, 
fc 



Viewing 

distance, 

ft 



Computed 
luminance, 
fL 1 ' 2 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



Reflec- 
tance, 

% 



Computed 

illuminance, 

fc 1 ' 3 



20- to 

30-yr- 

olds 



40- to 

60-yr- 

olds 



SHOVEL 1 



Seen from operator's cab: 
















Bottom rear of dipper 


















4.43 


30 


0.050 


0.083 


10.38 


0.49 


0.80 


Edge of loaded truck bed. 


7.22 


20 


.072 


.123 


10.39 


.70 


1.19 



SHOVEL 2 



Seen from ground level 
at boarding ladder: 
Handhold (rung) 



1.31 



1.3 



0.004 0.007 



6.11 



0.07 



0.11 



SHOVEL 3 



Seen from operator's cab: 
Bottom rear of dipper 
resting on ground 



1.28 



59.8 0.045 0.073 



42.97 



0.10 



0.17 







SHOVEL 4 












Seen from operator's cab: 
Bottom rear of dipper 

Seen from landing outside 
door to house: 


3.23 

2.48 
1.68 

.54 
.35 


52 

1.6 
3.7 

2.6 
1.3 


0.101 

.030 
.034 

.080 
.075 


0.173 

.048 
.054 

.135 
.125 


20.43 

1.61 
22.62 

20.37 
5.71 


0.49 

1.88 
.15 

.39 

1.31 


0.84 
2.98 


Edge of landing to de- 


.24 


Seen from ground level at 
boarding stairs: 


.66 




2.19 



SHOVEL 5 



Seen from operator's cab: 
Bottom rear of dipper 

resting on ground 

Seen from ground level at 
boarding ladder: 

Bottom rung . 

Handhold (rung) 



8.98 



4.40 
4.55 



22.8 



2.4 
1.5 



0.070 



,045 
.006 



0.119 



.073 
.010 



15.37 



25.45 
.66 



0.46 



.18 
.98 



0.77 



.29 

1.50 



SHOVEL 6 



Seen from operator's cab: 
Bottom rear of dipper 

resting on ground 

Seen from ground level at 
boarding ladder: 

Bottom rung 

Handhold (rung) 



4.19 



1.12 
.95 



23 



3.9 

1.8 



0.027 



.220 
.202 



0.043 



.411 
.373 



23.63 



26.78 
30.53 



Calculated for median age in each group. 

To convert to candelas per square meter, multiply by 3.426. 

To convert to lux, multiply by 10.76. 



0.11 



.82 
.66 



0.18 



1.54 
1.22 



28 



TABLE 14. - Illumination values resulting from task visibility measurements 
for noncoal mine blasthole drills 





Existing 
illumi- 
nance, 
fc 


Viewing 

distance, 

ft 


Computed 
luminance, 
fL 1 ' 2 ' 


Reflec- 
tance, 

% 


Computed 

illuminance, 

fc 1 ' 3 




20- to 

30-yr- 

olds 


40- to 

60-yr- 

olds 


20- to 

30-yr- 

olds 


40- to 

60-yr- 

olds 






DRILL 


1 






Seen from ground level: 4 
Wooden marker to align 
machine for drilling 


0.54 
.66 

10.51 
1.42 
3.47 


30 
41.3 

8 

2.2 
32 


0.093 
.425 

.090 
.022 
.150 


0.160 
.871 

.154 
.035 
.270 


16.67 
9.09 

9.99 
9.15 
2.59 


0.56 
4.68 

.90 

.24 

5.79 


0.96 




9.58 


Straw to mark hole 


1.54 




.39 
10.43 



DRILL 2 



Seen from operator's 
cab: 
Stem lock against 

drill pipe 

Red digit of pressure 

gauge 

Cardboard cylinder to 
maintain opening of 

blasthole 

Seen from ground level 
at boarding stairs: 

Bottom step 

Handrail 

Seen from landing at 
head of boarding 
stairs: Edge of land- 
ing to descend stairs.. 



5.28 
6.57 

1.18 



2.62 
2.28 



2.24 



7 
1.3 

10 



3.4 
2.2 



3.7 



0.093 
.486 

.050 



018 
,105 



.026 



0.159 
1.02 

.081 



,028 
,183 



.041 



41. 
66. 



67 
67 



11.02 



53 
51 



1.78 



,40 
.73 

.45 



16 
99 



1.47 



2.42 
1.53 

.73 



1.82 
5.20 



2.30 



DRILL 3 



Seen from operator's 
cab: Deck bushing 
(dust-coated) against 
drill pipe 

Seen from landing out- 
side door to house: 
Handrail 



13.90 



3.24 



7.2 



1.3 



0.029 



.037 



0.045 



.060 



10.50 



10.80 



0.27 



34 



0.43 



.56 



Calculated for median age in each group. 

To convert to candelas per square meter, multiply by 3.426. 
To convert to lux, multiply by 10.76. 

Operator worked alone and relocated the machine by remote control while standing on 
ground near operator's cab. 



29 



TABLE 15. - Illumination values resulting from task visibility measurements 
for noncoal mine loaders 





Existing 
illumi- 
nance, 
fc 


Viewing 
distance, 
ft 


Computed 
luminance, 
fL 1 ' 2 


Reflec- 
tance, 

% 


Computed 

illuminance, 

fc 1 ' 3 




20- to 

30-yr- 

olds 


40- to 

60-yr- 

olds 


20- to 

30-yr- 

olds 


40- to 

60-yr- 

olds 


LOADER 1 


Seen from operator's 
cab: Top rear edge 


4.47 


12 


0.080 


0.134 


25.28 


0.32 


0.53 


LOADER 2 


Seen from operator's 
cab: Top rear edge 


1.35 


13 


0.053 


0.086 


25.92 


0.20 


0.33 



Calculated for median age in each group. 

To convert to candelas per square meter, multiply by 3.426. 

To convert to lux, multiply by 10.76. 



2. On dozers and loaders, there is a 
need to improve visibility and illumina- 
tion in viewing areas immediately ahead 
of the machines and adjacent to either 
end of the blade or bucket, so that the 
overburden material sliding off to the 
right or left can be seen. Improvements 
in these areas can be made by assuring 
the proper aiming of the light beams of 
luminaires and/or replacing existing 
lamps with those of higher intensity. 

3. Two other examples involve machin- 
ery working near the highwall of the min- 
ing pit. A principal danger associated 
with the highwall is the potential for 
rocks and other loose material to fall or 
roll off these nearly vertical walls of 
overburden onto equipment, such as shov- 
els or loaders, working in the pit below. 
The danger at waste dumps or stockpiles 
is the potential for haul trucks to top- 
ple over the edge of the highwall and 
into the pit when dumping waste material. 
Illumination levels can be increased and 
the required visibility attained in these 
cases by using portable light plants 



(fig. 18), which are available at nearly 
all mines. The light plants, however, 
should be placed in locations that would 
minimize glare for equipment operators 
working in the areas. 

The use and application of the in- 
strumentation, methods, and equations 
presented in this report will enable a 
surface mining company to improve its ex- 
isting levels of luminance and illumi- 
nance on or about its mining equipment. 
Due to the wide variation in lighting at 
the different mines, the limited time 
available to take measurements on operat- 
ing equipment, and the limitations of the 
instruments used, the data given in the 
tables are only an indication of the 
luminances, illuminances, and reflectance 
factors needed for equipment operators 
to carry out required tasks safely and 
efficiently. 

The results of this study should pro- 
vide data useful in efforts to establish 
illumination standards for surface mines. 
Additional field work should be done to 
establish more rigid guidelines. 



30 




FIGURE 18— Typical portable lighting unit. 



REFERENCES 



1. Federal Register. U.S. Mining En- 
forcement and Safety Administration (Dep. 
Interior). Illumination. V. 2, No. 9, 
Jan. 13, 1977, pp. 2805-2807. 

2. Blackwell, H. R. Development of 
Procedures and Instruments for Visual 
Task Evaluation. Ilium. Eng. (N.Y.), v. 
65, 1970, pp. 267-291. 

3. . Instructions for Use of the 

Blackwell VTE Model 5 Visibility Meter. 
Aug. 1983, 10 pp.; available upon request 
from A. G. Mayton, BuMines, Pittsburgh, 
PA. 

4. Merritt, J. 0., T. J. Perry, W. H. 
Crooks, and J. E. Uhlaner. Recommen- 
dations for Minimal Luminance Require- 
ments for Metal and Nonmetal Mines (con- 
tract J0318022, Perceptronics, Inc.). 
BuMines OFR 65-85, 1983, 236 pp.; NTIS PB 
85-215689. 

5. Kaufman, J. E. (ed.). IES Lighting 
Handbook. Illuminating Engineering Soc. , 
New York, ref. v., 1981, 577 pp. 



6. Hitchcock, L. C. Development of 
Minimum Luminance Requirements for Under- 
ground Coal Mining Tasks (contract 
H0111969, U.S. Dep. Navy). BuMines OFR 
12-74, 1973, 288 pp.; NTIS PB 230 447. 

7. Commission Internationale de 
l'Eclairage (CIE), Technical Committee 
3.1 (Paris). An Analytic Model for De- 
scribing the Influence of Lighting Param- 
eters Upon Visual Performance. V. 1, 
Technical Foundations; v. 2, Summary and 
Application Guidelines. 
(TC-3.1), 1981, 235 pp. 

8. Blackwell, H. R. 
Laboratories). Private 
June 1985, 6 pp.; available upon request 
from A. G. Mayton, BuMines, Pittsburgh, 
PA. 

9. Kaufman, J. E. (ed.). IES Lighting 
Handbook. Illuminating Engineering Soc, 
New York, 5th ed. , 1972, pp. 3-14, 3-15, 
3-16. 



CIE Rep. 19/2 

(Visioneering 
communication, 



31 



APPENDIX A. --GLOSSARY OF TERMS. ABBREVIATIONS, AND SYMBOLS 1 



TERMS 

Equivalent contrast — a measure of the 
visibility of a visual task representing 
the luminance contrast of the reference 
task with both the visual task and refer- 
ence task having the same visibility at 
the background luminance level of the 
visual task. 

Illuminance — density of light flux ar- 
riving at a surface. 

Illumination — the act of illuminating 
or state of being illuminated. 

Luminance — a measure of the character- 
istic of being luminous, formerly called 
brightness. 

Luminance contrast — the difference in 
luminance of a visual task's critical de- 
tail and its immediate background, ex- 
pressed as a proportion of the background 
luminance. 

Reflectance — generally speaking, the 
ratio of the light flux leaving a surface 
to the light flux striking a surface. 

Threshold contrast — the value of lu- 

the visibility 



at 



mmance contrast 
threshold. 

Transmittance — the ratio of the light 
passing through a medium to the light 
striking the medium (illuminance). 

Visibility — the quality or state of be- 
ing perceived by the eye. 



References 5 and 7 were primarily used 



Visibility level — a measure of the ex- 
tent to which the equivalent contrast of 
a visual task exceeds the visibility 
threshold of an observer for the same 
display at the same level of task back- 
ground luminance. 

Visibility reference function — values 
of threshold contrast as a function of 
reference luminance for the visibility 
reference task, obtained by the reference 
observer. 

Visibility reference task — a 4 ' lumi - 
nous disk shown in a pulse train of 
0.2-s exposures when used to establish 
the visibility reference function. 

Visibility threshold — the setting on a 
contrast-reducing visibility meter at 
which the critical detail of a visual 
task can barely be seen, such as detec- 
tion of presence, recognition of spatial 
detail, recognition of meaning. 

Visual performance — generally speaking, 
the speed and accuracy with which a vis- 
ual task is performed. 

Visual task — the critical detail of ob- 
jects or surfaces that must be seen to 
perform a given activity and the imme- 
diate background of the objects or 
surfaces. 

Visual task evaluator — an optical in- 
strument that enables an observer to mea- 
sure visibility by varying the contrast 
of objects or surfaces seen through the 

instrument. 



in defining the terms and symbols. 



32 



ABBREVIATIONS AND SYMBOLS 

NOTE. — This list does not include the unit of measure abbreviations listed at the 

front of this report. 

C Luminance contrast 

C Threshold contrast 

CC Contrast control 

CIE Commission Internationale De L'Eclairage 

(International Commission on Illumination) 

C re f Reference equivalent contrast 

C re f Reference threshold contrast 

CT Contrast transmittance 

DVM Digital voltmeter — a numerical value corresponding to the measurement 
of a level of contrast with the Blackwell model 5 VTE. 

E Illuminance 

IES Illuminating Engineering Society of North America 

k j Correction constant for VTE model 5 

k Q VTE operator calibration constant 

L Standard population luminance 

Lb Background luminance 

L re f Reference luminance 

L-t Target (critical detail) luminance 

mi Visibility threshold multiplier for age 

M-NM Metal and nonmetal 

R Reflectance 

RCS re f Relative contrast sensitivity 

VL Visibility level 

VL/\ Adjusted visibility level 

VLr Raw visibility level 

VTE Visual task evaluator 



APPENDIX B. —CALIBRATION AND ANALYSIS PROCEDURES 



33 



CALIBRATION FOR THE VTE USER 

The following discussion is excerpted 
in part from Blackwell (8). 1 In order to 
adjust visibility data for differences in 
the sensitivity between a VTE user and 
the average 20- to 30-yr-old of the nor- 
mal population, a calibration constant, 
k , was determined for the Bureau VTE 
user. In the Bureau's illumination labo- 
ratory, a series of 10 tests was con- 
ducted using a black, matte, circular 
target on a white, matte-paper back- 
ground. The size of the target was ad- 
justed to the size of a 4' disk by in- 
creasing the distance of the user from 
the target. The adjustment was made by 
the formula 



4' target = j (3,436), 



where x = diameter of target, in; 



(B-l) 



and 



d = user distance, in. 



C = 



Lt 



L b 



(B-3) 



where Lb = luminance of the background; 

and L-t = luminance of the target. 

Then, the VTE user's threshold contrast 
for a 4' disk target under VTE model 5 
conditions is 



C = (C)(CT). 



(B-4) 



Using the external luminance (Lb from 
above) and the graph in figure B-2, the 
threshold contrast C np can be obtained 
for the average normal user in the 20- to 
30-yr-old age group. Note that the graph 
takes into account the overall transmit- 
tance (0.08) of VTE model 5. The user's 
calibration constant is given then by 



ko - Cnp/C( 



(B-5) 



Once the test target was set up, a to- 
tal of 10 VTE readings were taken (that 
is, the contrast control dial was set to 
visibility threshold 10 times). Values 
in degrees were read from the contrast 
control of the VTE and were converted to 
digital voltmeter units (DVM) by the 
equation 

CC = 350 - 40 DVM, (B-2) 

where CC = contrast control reading, 
deg; 

and DVM = unit of measure of threshold 
contrast. 

The DVM values were summed, averaged, and 
then used in conjunction with the graph 
in figure B-l to obtain a value of CT. 
The luminance contrast C was determined 
for each test by the equation 

Underlined numbers in parentheses re- 
fer to items in the list of references 
preceding appendix A. 




.004 



I 2 3 4 5 6 7 

DIGITAL VOLTMETER READING (DVM) 



FIGURE B-1 .—Contrast control calibration for VTE model 5. 
(Courtesy H. R. Blackwell, Visloneerlng Laboratories) 



34 



o 10 

LU CO 

a: < 

•— • z 
o o 
Q o 



t 1 1 r 



t r 



i 1 r 



-i r 



fc—x- 



-1.5 



J L 



J I L 



J L 



i I i 



J L 



1.0 



1.5 2.0 2.5 

LOG [EXTERNAL LUMINANCE, cd/m 2 , x0.08] 



3.0 



FIGURE B-2 — Normal population data to determine calibration constant for users of VTE model 5. (Courtesy H. R. Blackwell, 
Visloneering Laboratories) 

A sample of calculations to determine k D for 1 of the 10 laboratory tests follows: 

L>t and Lb were measured with a Pritchard photometer and found to be 2.11 fL and 40.6 
fL, respectively. The task contrast is calculated as 



C = 



40.6 - 2.11 



40.6 

= 0.948. 

The VTE's contrast control dial was set to visibility threshold 10 times, to give an 
average value of 1.88. From figure B-l , at DVM = 1.88, CT = 0.073. The VTE user's 
threshold contrast is then 

C = (0.948)(0.073) 

= 0.0692. 

Next, the external luminance (Lb) is changed to SI units: 

(40.6 fL) (3.426 C ^ m j = 139.1 cd/m 2 . 

Taking into account the 8% transmission of the VTE and taking the logarithm gives 

(139.1)(0.08) = 11.13; 

log 11.13 = 1.05 

From figure B-2 the log of the external luminance equal to 1.05 corresponds to log 
-1.19 for C np . 

The antilog of this value is 0.0646. Then k = "0*0592 ' 

= 0.9335. 

Thus, this value and those calculated for nine other lab tests gave an average val- 
ue of 0.97 for k . 



35 




-3 -2 -I +1 t2 +3 

LOG [EXTERNAL LUMINANCE, cd/m 2 ,xQ08] 

FIGURE B-3.— Correction constant for VTE model 5. (Courtesy H. R. Blackwell, Visioneering Laboratories) 



+4 



ANALYSIS OF FIELD DATA 

The field data, which included raw visibility level (VLr) values for the different 
mining tasks, were adjusted further to take into account the difference between the 
visual conditions of the model 5 VTE and the single-glimpse conditions used in CIE 
Report 19/2. The differences are the reduction in luminance imposed by the VTE and 
the use of long exposures rather than 0.2-s pulses. Using the graph in figure B-3 
with the logarithm of the external luminance measured for each task in the field, a 
correction constant for the VTE model 5, kj, was determined. Then the adjusted visi- 
bility level values (VLa) were calculated by 



VL A = VLr 



(£> 



(B-6) 



The visibility data collected during mine visits were analyzed according to the 
indirect method of CIE Report 19/2. The illumination levels for each mining task 
were computed by the equations that follow. Their use is shown in a set of sample 
calculations. A full explanation of the method can be found in CIE Report 19/2. 



C ref = 0.05936 



1.639 \ ' 4 
L ref J 



+ 1 



2.5 



(B-7) 



VL = Cref/Cref. 

~ f RCSref \ 
VL - L re f ^ 0.0923 m, ) 



(B-8) 
(B-9) 



36 

Age: 20-42 yr, mi = 1.000 + 0.00795 (A-20) , 

42-64 yr, m, = 1.175 + 0.0289 (A-42), (B-10) 

where m] = the visibility threshold multiplier, 

and A = age, yr. 

T / 1.639 \°» 4 1 " 2 « 5 

> r8 f = 1.555 [ { ±Z jf 1 ) + 1 " (B-ll) 



RCSr 



Using the equations above, the illumination levels for each mining task were calcu- 
lated, as illustrated in the following sample calculations. The L^, measured for each 
mining task is first converted to candelas per square meter and then can be used 
in equation B-7 for L re f to obtain a value of C re f» In this case, Lb was equal to 
0.03426, so: 

C ref =0.5936 [(^§39_)°- 4 + l] 2 - 5 

= 4.6. 

Using equation B-8 with this value of C re f and a value of 2.2 for VL (equivalent to 
VLa), C re f can be found. 

Cref = (2.2X4.6) = 10.1. 

This value of C r ef is subsequently inserted into equation B-9 with VL = 8.0 and mi 
= 1.040 (from equation B-10, where A ■ 25) to determine the appropriate value of 

RCSpef . 2 

wpc (0.0923)(8.0)(1.040) 
RCS ref - (10>1) 

- = 0.076. 

The luminance of the task is then calculated by substituting the resulting value of 
RCS re f into equation B-ll, which is rearranged to solve for L. 



L = 1.639 



\ 0.076 J 



0.4 

- 1 



-2.5 



= 0.195 cd/m 2 , 

or (0.195 cd/m 2 )(0.292) = 0.057 fL. 

This is the luminance level of the task for the average 25-yr-old user of the nor- 
mal population. 

— . 

■'A VL of 8 is the visual performance criterion used in the IES method for prescrib- 
ing illumination (9). 



37 



The illuminance or the amount of illumination on the task is computed by using the 
luminance or reflectance factor (R) of the task background under actual lighting 
conditions (also reference conditions). In this instance, R is 1.25%. Since the 
surfaces are largely diffusing, the equation describing a basic law of lighting can 
be used: 

L 



R = 



(B-12) 



where L = luminance; 
and E = illuminance. 
Inserting the values produces 



E = 



0.057 fL 



or 



0.0125 
= 4.56 fc, 
(4.56 fc)(10.76) = 49.1 lx. 



The level of illumination was also calculated for the most commonly found older 
worker. A random sample of 81 equipment operators was collected from 7 surface coal 
mines during the study. Of this total, 38% were found to be in the 40- to 60-yr age 
group. 

Using equation B-10, and 50 yr as the average age of this group, the factor mj is 
determined as follows: 

mi = 1.175 + 0.0289 (50 - 42), 

= 1.406. 

A new value of RCS re f is then calculated with this value of mi and the previously 
determined C re f. 

pro (0.0923)(8.0)(1.406) 
RCS re f = r^r— ^ — — > 



(10.1) 



= 0.103. 



As shown in the previous calculations for the 20- to 30-yr age group, this value of 
RCS re f is entered in equation B-ll to obtain the task luminance, which in this case 
was 0.304 cd/m 2 or 0.089 fL. Then, once again with 1.25% as the reflectance, 7.12 fc 
or 76.6 lx was calculated as the illumination on the task. 

Note that the preceding calculations for illumination did not account for other 
factors (discussed in CIE Report 19/2) that affect task visibility and, consequently, 
illumination, such as contrast rendition, disability glare, and transient adaptation 
effects. Inclusion of these additional factors in calculating illumination required 
additional measurements that were beyond the scope of this study. 



10783 96 



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